This proposal is concerned with examining the effects of changes in ambient temperature (Ta) on neuropharmacological manipulations of sleep states. Sleep, especially rapid eye movement (REM) sleep, is easily disrupted by any stress. A drug treatment that alter thermoregulation may alter an animal's zone of thermal comfort, thereby making the Ta at which sleep is being measured more stressful, and because of that, decrease or even eliminate REM sleep. We will examine the effects of Ta on sleep after administration of drugs that affect noradrenergic pathways in the brain. The experiments involve measuring sleep and body temperature (Tb) at two different Ta's, one below and one at or above a normal rat's thermoneutral zone, after injection of relatively specific agonists and antagonists of noradrenergic transmission. We will use clonidine as a specific alpha-2 agonist and phentolamine and yohimbine as the antagonists. We will examine not only the correlation between Tb and sleep, but also, by using behavioral thermoregulation, see whether a compound that changes Tb is doing so by altering the regulated level of Tb. We will also measure reflexive thermoregulatory responses to see if they are coordinated with each other to produce the changes in Tb. In view of the amount of effort that goes into trying to understand and treat sleep disorders, especially insomnia, this research should prove useful and timely, and takes a unique approach to these problems.